Method of making dynamo-brushes.



GEORG PREUSS, OF GHARLOTTENBURG, GERMANY.

IDETHOD OF MAKING DYNAMO-BRUSHES.

Specification of Letters Patent.

Application filed July 31, 1906.

Patented Dec. 15, 1908.

Serial No. 328,573.

To all whom it may concern:

Be it known that I, Gnono Pnnuss, an en %ineer, subject of Prussia, residing at 48 antstras'se, Charlottenbur ,Germany, have invented new and useful mprovements in Methods of Making Dynamo-Brushes, of which the following is a specification.

In making such dynamo-brushes as consist of carbon and metal, the attainment of an intimate cohesion between the carbon and metal causes difiiculties, while such a cohesion is absolutely necessary to make such brushes fit for use.

The present method relates to a manner of making dynamo-brushes which consist of carbon and metal in intimate combination. In accordance with my present invention the a bite is used in a state-like that obtained yt e so called nitric acid reaction. Namely, if graphite is moistened with nitric acid and afterwards heated, it swells up considerably and worma-like forms, which under some circumstances are many centimeters in length,

are formed. It may be possible to obtain such form of graphite with another treatment than the above described. These forms are extremel plastic and are provided electrically or otherwise with a metal coating. The reaction mentioned, by which also a purification of the graphite is obtained, does not appear with every carbon having the appearance of graphite, but only with ure raphite as distin ished from socalle grap ite. The graphite-metal bodies produced without any organic agglutinants in the manner described which are of great plasticity, are now ressed in molds either heating them so consi' erably that the softenin metal firmly combines or with less heating olding them together in a bon-brushes conduct the electric currents very well, rotect the commutatorandwear away ver ittle.

What claim as my invention, and desire to secure by Letters Patent, is

1. In a method of making dynamo-brushes consisting of carbon and metal the process of moistening pure graphite with nitric acid and afterwards heating the same, the graphite forms resulting by this treatment being provided with a metal coating, this combination of graphite and metal bemg then pressed in molds, substantially as described.

2. In a method of making dynamo-brushes consisting of carbonand metal the process of moistening pure graphite with nitric acid and afterwards heating the same, the graphite forms resultin by this treatment being provided electricafil with a metal coating and thenformed and ressed to brushes, substantially as describe 3. In a method of making dynamo-brushes consisting of carbon and metal the process of moistening the graphite with nitric acid and afterwards heating the same, the graphite forms resulting by this treatment being provided with a metal coating, this combination being then intensely heated and formed and pressed to brushes, substantially as described.

In testimony whereof I have signed my name to this specification in the presence of two subscribing witnesses.

GEORG PREUSS.

Witnesses OSKAR ARENDT, HENRY HASPER. 

